Companies and the like use a cluster system to allow operations to be continuously performed in the event of a system fault. In the cluster system, a plurality of server apparatuses are connected to one another, and these server apparatuses act as if they collectively represent a single server apparatus for a user.
Furthermore, in the cluster system, a fault is detected through heartbeat communication between the server apparatuses so as to prevent stoppage of operations (for example, see Patent Documents 1 and 2). In heartbeat communication, the server apparatuses transmit a signal indicating a self-presence (hereinafter referred to as a “heartbeat”) to one another at a set interval.
Specifically, in the systems disclosed in Patent Documents 1 and 2, each server apparatus first determines whether a timeout has occurred in heartbeat communication with respect to each communication path. When a timeout has occurred, it is determined that some sort of fault has occurred. When it is determined that a fault has occurred, each server determines whether a reception packet arrived within a set timeout period through a network. If the reception packet did not arrive (timeout), it is determined that a communication fault has occurred. If the reception packet arrived, it is determined that an abnormality has occurred in a partner server.
In the systems disclosed in Patent Documents 1 and 2, upon detection of the occurrence of a fault, a fault-free server apparatus takes over operations of a server apparatus with the fault. This prevents stoppage of the operations.